WASHINGTON (Reuters) - Salix Pharmaceuticals' diarrhea drug Xifaxan (rifaximin) should be cleared to treat patients with hepatic encephalopathy, but more study would still be needed after approval, a U.S. Food and Drug Administration advisory panel said on Tuesday.

The FDA's outside advisers, in a 14-4 vote, said the antibiotic appeared to help patients with the liver condition, but that the company's single clinical trial did not look at the sickest patients or follow subjects long enough given that the drug would be used until patients get a liver transplant or die. Even those backing approval called for additional trials or further patient monitoring.

Despite those concerns, "clearly, the potential benefits outweigh the risk," said panelist Dr. Richard Haubrich of the University of California, San Diego.

FDA officials will weigh its panel's recommendation before later making their final decision, expected by March 24.

The FDA is weighing the new use as an "orphan" product for rare conditions, but at least one panelist pointed to potential broader use as the number of liver problems grows in the United States. Dr. Alan Lockwood, a neurologist at Buffalo General Hospital in New York, said he expected wider use with cirrhosis.

"If it ultimately comes to approval it will surely be used by clinicians everywhere in patients who are much, much sicker," said panelist and Pennsylvania physician Dr. Steven Solga.

Panelists also said, if approved for the liver use, Xifaxan's label should call for it to be used in conjunction with lactulose.

Xifaxan is already FDA-approved for so-called travelers' diarrhea caused by certain strains of Escherichia coli. Salix is also studying it for other types of diarrhea and irritable bowel syndrome.